Effects Of Hpp On Foodborne Pathogens - Brief Article

Nutrition Research Newsletter, Feb, 2001

As there is a growing concern for food safety, there is also an increasing demand for minimally processed, fresher tasting, additive-free foods. Since heat pasteurization kills foodborne pathogens but does alter the taste of foods, an alternative food processing technique needs to be considered. High hydrostatic pressure (HPP) has recently been shown to be an effective method of killing enteric pathogens in certain foods without deleterious effects on nutritional value and taste.

Traditional salsa is usually highly acidified and heat processed to ensure safety and shelf-life stability, but recently several non-pasteurized salsa products have appeared in markets as refrigerated, high-cost items with limited shelf life. Since this unpasteurized salsa presents a potential public health hazard because of the increased tolerance of foodborne pathogens to low-pH foods, a current study was conducted on the effects of HPP on salsa. The study, conducted over a two-year period, examined the efficacy of HPP application to inactivate strains of Escherichia coli O 157:H7, Listeria monocytogenes and Staphylococcus aureus in salsa, while assessing the viability of HPP as a batch and semicontinuous food production process.

The salsa was evaluated for the survival of the inoculated pathogens following HPP treatment and after storage at 4 [degrees] C and 21 to 23 [degrees] C for up to two months. Salsa samples also inoculated with the foodborne pathogens but that did not undergo HPP treatment were stored under the same conditions and evaluated to determine the effects of the acid environment of salsa on the inoculated strains.

In the non-HPP-treated salsa, storage at refrigeration temperature resulted in an increase in the time of survival. Inoculated pathogens were detected in the non-HPP-treated samples stored at 4 [degrees] C after one month, with L. monocytogenes showing the longest survival at both refrigeration and room temperature storage. Also in the non-treated samples at the temperature of 21-23 [degrees] C, E. coli and S. aureus were not detected after one week, but L. monocytogenes was detected in low levels. None of the inoculated pathogens were detected in the HPP-treated samples for all treatments throughout the storage period. None of the nonpathogenic microorganisms were recovered after semicontinuous HPP treatment as well.

These results show that HPP treatment in the low-pH salsa ended in total inactivation of the inoculated pathogens and may be a good choice in the future for food safety. The findings also revealed that this inactivation is the same in a batch or semicontinuous HPP treatment system.

Errol V. Raghubeer, C. Patrick Dunne, Daniel F. Farkas, and Edmund Y. Ting, Evaluation of Batch and Semicontinuous Application of High Hydrostatic Pressure on Foodborne Pathogens in Salsa, Journal of Food Protection 63(12): 1713-1718 (December 2000) [Correspondence to: Errol V. Raghubeer, Flow International Corp., 23500 64tn Ave. S., Kent, WA 98032. Phone: 253-813-2747. Fax: 253-813-3322. E-mail: eraghubeer@flowcorp.com].